A 3-year-old child with sickle cell disease (HbSS) has acute chest syndrome. The pathophysiological mechanism underlying acute chest syndrome is:

• A Autoimmune destruction of alveolar epithelial cells by anti-HbS antibodies
• B Vaso-occlusion of pulmonary microvasculature by sickled RBCs, compounded by fat emboli from bone marrow infarction and infection ✓
• C Hypersplenism causing trapping and destruction of sickled RBCs in pulmonary sinusoids
• D Pulmonary hypertension from chronic sickling causing fixed right-to-left shunting

Explanation

Acute chest syndrome (ACS) is the most common cause of death in sickle cell disease and is defined by new infiltrate on CXR, fever, and respiratory symptoms. It is multifactorial: pulmonary microvascular vaso-occlusion by sickled RBCs causing ischemia, fat embolism from infarcted bone marrow, pulmonary infection (Streptococcus pneumoniae, Chlamydia, Mycoplasma), and hypoventilation from painful splinting all contribute. The resultant hypoxia further promotes sickling, creating a vicious cycle. Exchange transfusion is often needed to reduce HbS percentage.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.